[The luminal surface of the rat trachea during ontogenesis]

To complete the hitherto existing results about the trachea epithelium, the scanning electron microscope was used to get representative statements about the apical surface of the epithelium: First of all the epithelium consists of undifferentiated round cells with cytopodia. The cells rarely carry single cilia at the same time. At the 18. day of pregnancy nearly all of the cells have a single cilium. Until the end of the intrauterine phase the single cilia are retracted again. At the 20. day ciliated cells and cells with protrusions are formed. Mucus granula are secreted into the lumen already before birth. Immediately post partum much mucus appears. Its distribution, viscosity and optical behaviour is different. For ciliated cells and goblet cells no special characteristical distribution was noticed. The building of the cells surface was detailed discussed. The question about function of the single cilia cannot yet be answered.